This invention relates to a microwave modulator capable of both amplitude and phase modulation and, more particularly, to the use of plural couplers with electronically adjustable terminating resistors to provides for a full 360 degrees of phase shift and a capacity for varying amplitude through zero amplitude, the amplitude and the phase being independently adjustable to allow the modulator to be used also as a phase shifter and an attenuator, as well as for a single side-band up-converter and down-converter.
Various forms of microwave phase shifters and attenuators are known. The phase shifters may be formed of a set of pin diodes, by way of example, for electronic phase shifting as well as for phase modulation. Mechanical devices, such as movable vanes, by way of example, may be employed in the construction of both phase shifters and attenuators and, by moving the vanes either manually or by motors, phase shift and/or attenuation may be varied, and a slow modulation of phase and/or amplitude may be attained.
A problem arises in that in modern signal processing and communication systems, rapid phase shift and amplitude variations may be required, and phase shifts through a range of 360 degrees may be desired. It is advantageous, furthermore, if a single device capable of providing the foregoing modulations can be used also as an up-converter or down-converter of a carrier frequency of a microwave signal. Presently available circuitry does not provide all of these functions.